1. Field of the Disclosure
The present disclosure relates to power control systems, and more particularly to adaptive power control systems that do not require factory calibration of loop control parameters.
2. Description of the Related Art
In current power control systems, transmit (Tx) power ramp up and down curves are controlled by altering the control or bias voltage applied to a power amplifier or a voltage controlled amplifier (VCA) modulator integrated circuit. For example, the controls to meet power control specification requirements, such as power versus time and transient adjacent channel power masks for GSM-FracN, WCDMA, and Cartesian IQ multiple access modes, are typically performed by a closed loop power control system.
Current closed loop power control systems require extensive factory calibration because the control voltage applied versus the transmit power output characteristics of the power amplifier or VCA stage as well as that of the power detection feedback path vary depending on the frequency band of operation, the input power level to the power amplifier, and variations in temperature and battery voltage.
Because of tri-band requirements (GSM, DCS or the PCS bands) of some systems, the slope of the control voltage versus the transmit power out characteristics changes with each frequency band of operation. In addition, the power amplifier transmit power versus the detected power characteristics of the power detector also vary with the different bands of operation.
The slope of the control voltage versus transmit power output curve varies with respect to input power levels (dBm) at the power amplifier. Prediction of variations of the power input to the power amplifier and programming of corresponding system parameters is difficult. The slope of control voltage versus the transmit power output curve also changes with temperature and battery voltage variations.
In order to meet loop stability and performance requirements including power versus time mask and switching transient specifications, different AOC system parameters, for example, loop bandwidths and the analog feedback gains, have to be programmed for each frequency band of operation, for different power inputs, and for different temperature and battery voltage variations. Typically, pre-calibrated fixed settings for the loop bandwidths during transmit ramp up and ramp down are used. The factory calibration of the power control loop bandwidths is a complex task which has to be performed as a function of the frequency band of operation, input power levels to the power amplifier, initial and final target power level, temperature, and supply voltage. Factory calibration is time intensive and costly.
A transmit power control system which does not need extensive factory calibration of power control loop bandwidths over the power transition ranges, frequency bands of operation, temperature and supply voltage is desired.
The use of the same reference symbols in different drawings indicates similar or identical items.